Method and device for detecting the state of an air filter of an air conditioning system

ABSTRACT

A method and a device detects the state of an air filter in an air conditioning system for the interior of a motor vehicle. Condensed water created at the evaporator is discharged and fed to a sensor, which determines a parameter of the condensed water, and which, from a change or a certain value of the measured parameter, draws a conclusion regarding a change of the state of the air filter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention pertains to a method for detecting the state of an air filter in an air conditioning system for the interior of a motor vehicle. Furthermore, the invention pertains to a corresponding device for carrying out the method for detecting the state of an air filter of an air conditioning system for the interior of a motor vehicle and to an air conditioning system for a motor vehicle.

2. The Prior Art

Air filters, such as pollen filters or, in particular, activated carbon filters, for example, are integrated in such air conditioning systems. The problem with active carbon filters is that even though the filters are superbly suitable for absorbing pollutants, they only have a limited absorption capability. If an active carbon filter reaches the limit of its absorption capability, it begins to release pollutants, which it had already absorbed. It is thus necessary to replace the filter before this occurs. The filtering capability of other filters also decreases after an extended operating time or the air resistance increases, and the efficiency of the air conditioning system is impacted. It is known from European Patent No. EP 0908341 B1 to detect a parameter of the air, which passes through the filter, and to compare this value with a reference value, and to determine therefrom, whether or not the filter must be replaced.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a method and a device of the above-mentioned type, with which a particularly simple and reliable inspection is possible.

According to the invention, the state of an air filter in an air conditioning system for the interior of a motor vehicle is detected by supplying the condensed water created in the air conditioning system to a sensor, which detects at least one physical characteristic of the condensed water. From the value detected by the sensor, there is derived a statement regarding the state of the air filter. The invention realizes the idea that the air absorbed from the environment in the air conditioning system or the HVAC system is initially guided through a filter, for example a pollen filter or an active carbon filter, and is then guided through the evaporator of the air conditioning system, which cools the temperature of the air. In so doing, moisture in the air condenses at the evaporator and is discharged as condensed water. This condensed water created downstream from the filter, which is to be tested, thus contains an amount of pollutants or dirt particles, which is directly correlated with the state of the filter. It is thus proposed according to the invention, to test the condensed water instead of the air, as this can be carried out in a comparatively simple manner.

Preferably, the sensor detects a physical variable of the condensed water or a parameter, which is determined by one or a plurality of physical variables of the condensed water, such as leak tightness, permeability, viscosity, and temperature, for example. Preferably, an electric field is formed, which is influenced by the condensed water, which is guided through this electric field, and the sensor detects a change of the electric field. In another preferred embodiment of the invention, the sensor detects a changing oscillation behavior of an oscillating element in the condensed water. A tuning fork, for example, is used for this purpose. Other measuring methods for detecting parameters or physical characteristics of the condensed water are also possible.

In a preferred embodiment of the invention, the detected value is tested with reference to a temporal change of the detected value. In the alternative, the detected value is compared with a reference value. A statement regarding the state of the filter is then derived from the change of the detected value or from the deviation from the reference value.

In the device for detecting the state of an air filter of an air conditioning system for the interior of a motor vehicle with a condensed water discharge, which carries out the above-mentioned method, it is essential to the invention that a sensor for determining a parameter of the condensed water is disposed in the condensed water discharge.

Preferably, the sensor is disposed in the bottom area of a container, which is filled with discharging condensed water. The container, in turn, has a further discharge. Preferably, a level sensor, which checks the level and thus ensures that the discharge of the condensate occurs, is integrated in the container.

Preferably, the sensor detects physical characteristics of the water, such as, in particular, the leak tightness, the permeability, the viscosity, and the temperature or of a parameter, which is influenced by these values, which, in turn, are again influenced by the contents of the water and, in particular, by the dirt particles. Preferably, the sensor comprises a capacity. Said capacity can detect an electric field applied in the container or its change. In another preferred embodiment, the sensor has an interdigital resistor, which also detects an electric field applied in the container or its change. Interdigital resistors essentially consist of two conductors, which are isolated from one another, which engage with protrusions offset in a duct-like manner. In another preferred embodiment, the sensor comprises an oscillating element, for example a tuning fork, the frequency behavior of which is a function of the characteristics of the ambient condensed water.

Another aspect of the invention is the provision of an air conditioning system for a motor vehicle, that comprises an air filter and a condensed water discharge at the evaporator, and a sensor of the above-mentioned type is disposed in the condensed water discharge. An additional aspect of the invention is that a motor vehicle is provided with an air conditioning system that has an air filter and a condensed water discharge at the evaporator, and a sensor of the above-mentioned type is disposed in the condensed water discharge.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawing. It is to be understood, however, that the drawing is designed as an illustration only and not as a definition of the limits of the invention.

The sole FIGURE of the drawing illustrates a part of an air conditioning system in a HVAC system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The sole figure of the drawing illustrates a part of an air conditioning system 1 in a HVAC system 1 (heating, ventilating, air conditioning). In the right-hand area of this HVAC system 1, air is supplied into the system via a supply 3 by means of a ventilator 2. The system comprises a filter 4, an evaporator 5 of the air conditioning system and, normally, a heat exchanger 6 for the possible heating of the air, which is guided through. In the left-hand area, the air is guided through ducts 11 to the fan nozzles. In addition to the evaporator, the air conditioning system itself comprises further, non-illustrated components, i.e. in essence, a condenser, a pump for driving the cooling means, and a compressor for condensing the cooling means. Typically, a discharge 7 for condensed water is disposed below evaporator 5 of the air conditioning system. Said discharge fills a container 8, in which a sensor 9 is disposed. Preferably, sensor 9 is disposed in the bottom area. Sensor 9 measures a parameter of the condensed water, which is influenced by the physical variables, such as leak tightness, permeability, viscosity, and temperature of the condensed water, and also by the dust or dirt content of the condensed water. A predetermined change of the measuring value or a predetermined deviation from a reference value is detected by a corresponding electronic circuit and it derives therefrom a statement regarding the state of the sensor. Preferably, the electronic circuit is integrated in the housing of the HVAC system 1. Preferably, a level sensor, which ensures that the discharge of the condensed water actually takes place via line 10, is also disposed in the container 8.

Accordingly, while only a few embodiments of the present invention have been shown and described, it is obvious that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention. 

1. A method for detecting the state of an air filter in an air conditioning system for the interior of a motor vehicle, comprising the following steps: feeding condensed water created at an evaporator of the air conditioning system to a sensor; detecting with the sensor at least one physical characteristic of the water represented by a value; and deriving a statement regarding the state of the air filter from the value detected by the sensor.
 2. The method according to claim 1, wherein the sensor detects a change of an electric field.
 3. The method according to claim 1, wherein the sensor detects a changing oscillating behavior of a tuning fork.
 4. The method according to claim 1, wherein the detected values are checked regarding a temporal change of the detected value.
 5. The method according to claim 1, wherein the detected value is compared with a reference value.
 6. A device for detecting the state of an air filter in an air conditioning system for the interior of a motor vehicle, comprising: a condensed water discharge; and a sensor disposed in the condensed water discharge.
 7. The device according to claim 6, wherein the sensor detects physical characteristics of the water.
 8. The sensor according to claim 6, wherein the sensor has a capacity.
 9. The device according to claim 6, wherein the sensor has an interdigital resistor.
 10. The device according to claim 6, wherein the sensor has a tuning fork.
 11. The device according to claim 6, wherein the sensor is disposed in a container that is connected to the condensed water discharge.
 12. The device according to claim 11, wherein the sensor is a level sensor.
 13. An air conditioning system for a motor vehicle comprising: an evaporator; a condensed water discharge disposed in an area of the evaporator; and a sensor disposed in the condensed water discharge.
 14. A motor vehicle with an air conditioning system comprising: an evaporator; an air filter; a condensed water discharge disposed in the area of the evaporator; and a sensor disposed in the condensed water discharge. 